Normal vision occurs when light that passes through and is refracted by the cornea, the lens, and other portions of the eye, and converges at or near the retina. Myopia or near-sightedness occurs when the light converges at a point before it reaches the retina and, conversely, hyperopia or far-sightedness occurs when the light converges a point beyond the retina. Other abnormal conditions include astigmatism where the outer surface of the cornea is irregular in shape and effects the ability of light to be refracted by the cornea. In addition, in patients who are older, a condition called presbyopia occurs in which there is a diminished power of accommodation of the natural lens resulting from the loss of elasticity of the lens, typically becoming significant after the age of 45.
Corrections for these conditions through the use of implants within the human cornea have been suggested. Various designs for such implants include solid, ring shaped, and split-ring shaped, circular flexible body members and other types of ring-shaped devices that are adjustable. These implants are inserted within the body of the cornea for changing the shape of the cornea, thereby altering its refractive power.
Generally, the human cornea flattens away from the center. The reasons are not completely clear, though one known factor is that as the cornea flattens it reduces the spherical aberration. Therefore, I consider it desirable to reshape the cornea and maintain an aspheric surface that naturally occurs while correcting for refractive error. I believe there is a demonstrated need for a more effective corneal implant that has an aspheric surface that will correspond more naturally to the surface of the human eye to address the problems as previously discussed.